drm/radeon/kms: don't enable connectors that are off in the hotplug handler

If we get a hotplug event on an connector that is off, don't
attempt to turn it on or off, it should already be off.

Fixes:
https://bugzilla.redhat.com/show_bug.cgi?id=728228

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/radeon_connectors.c

@@ -60,6 +60,10 @@ void radeon_connector_hotplug(struct drm_connector *connector)
 
 	radeon_hpd_set_polarity(rdev, radeon_connector->hpd.hpd);
 
+	/* if the connector is already off, don't turn it back on */
+	if (connector->dpms != DRM_MODE_DPMS_ON)
+		return;
+
 	/* powering up/down the eDP panel generates hpd events which
 	 * can interfere with modesetting.
 	 */